Issue 2: The process has evolved a lot in a couple months. Now, you can just run a single .app against a thumbdrive that’s been “Restored” with the 10.5.6 dmg, and it will take care of the rest. That app is called NetbootBootMaker.app. Info on that can be found here: http://osx.mechdrew.com/guides/nbi1.shtml

Other than that, it seems pretty cut and dry. The only issue I had was rebooting after installing the 10.5.8 Combo update. It seems to need the thumbdrive attached when that is done.